Razor blade and steel therefor



' ness of blades that is, described in United States Patented Jan. 1 8, 193s PATENT, OFFICE nazon BLADE AND STEEL 'r nnnnron Elbrldge 1'. ,Casselman, Pittsburgh, Pa, assignor to Magazine Repeatin poration of New Jersey I Razor Company, a cor- No Drawing. Application January 13, 1937,

Serial N0. 120,404

1 Claim. (01.30-350) This invention relates tosteelalloys, and consists inan alloy of unique composition and'ln a razor blade of superior excellence produced there- 'from'. Thisabplication is a continuation in part Of an application filed by me February 29, 1936, Serial No. 66,440. v

The invention has particularly to do with the productionof razor blades of ribbon type. In order to produce these articles the material of which they are made must be susceptible tobeing rolled to ribbon form; it must be susceptible ,to hardehingjin heat-treating furnaces of continuous type; it must be susceptible to sharpening in continuous machinery. All these characteristics are requisite to large-scale production, And the blade that ispr'oduced must have durability in'sharpne'ss of edge.

I have made extensivestudy of the qualities of razor blades produced from steels and steel alloys of various composition. In this study I have employed the machine for testing the sharp- Letters Patent No. 1,983,597, granted on my application December 11, 1934; and I have discovered facts'not heretofore known about thesharpness of the edges of razor blades. The procedureof my study was thisz-The sharpness of I each blade under study was first measured, and its edge was examinedunder the microscope.

shavers, upon whom prior determination had been made and determination reached with ac-.

} curacy, whatgrelatively were the dulling effects of these individuals in their use of razor blades in; Shaving: After each shave thexsharpness of the blade was again measured and the blade was again examined microscopically, andrecord was made of the report of the shaver as to the comfort and'th'e-ease of shaving. The blades after use wereset aside and. were used again after periodso'f rest that ranged from five minutes to several days.

By such study .I discovered that chromium is uniqueamong the constituents oi: steel alloys in proionging the useful life of razor blades. In the course of study the following particular matters came to. light:' 7

' I differences are found to exist in the ease ,with which the blades may be sharpened- The tougher and the" softer the substance ofthe blade, the more dimculti itis to sharpen it.

2. It is characteristic of blades formed of carbon steel that the degree of dulling per shave isdirectly related to the minute formation of 'the edge. For example, if the beveled margin of the blade is 0.001 inch wide, and if upon this margin an edge of 45 be imposed, sharpness will be less durable than if a 40 edge be Zimposed on a beveled margin 0.0003 inch wide.

3. It is a further characteristic of blades formed of carbon steel that the rate of dulling, though fairly constant during the earlier part of the term of useful life, increases rapidly toward the end of the term. The blades change rapidl from useful to useless condition.

4.'In the case of blades formed of chromium greater. the difllculty of overcoming the toughness that hinders and of attaining the hardness steels, the larger the chromium content, the

ened to a angle and a blade with a 0.0003

inch margin sharpened to a 40 angle, durability was found to be equally as good in the two cases. The blades were then used repeatedly by trial 6.'It is characteristic of a razor blade formed of chromium steel that the rate of dulling, instead of increasing, actually diminished toward changes slowly from useful to useless condition. 7. Specifically, I discovered that in the case of razor blades formed of chromium steel alloysin which the chromium content is as great as 6% and in which the carbon content is as great as 1%, though in no case as great as 2%, durability of sharpness is attained and the regeneration of sharpness, that in other cases progresses slowly as the blade rests idle after use, progresses with relatively great rapidity; that further increase, beyond 6%, .of the magnitude of the chromium content has little or no effect in hastening the recovery of sharpness; that increase to as much I as 8% is undesirable, in that the difiiculties of rolling. lardening, and sharpening are too great- 1y increased; and that best results for use in razor blades are attained when the chromium content ranges from 6 upward but is less than 8%, while the carbon content is at least 1%.

.Decrease of the carbon content below 1% has efiect in increasing the difilculties of hardening and f sharpening.

the end of the useful life of the blade. The blade I believe myself to be the discoverer of the phenomenon that razor blades of chromium steel, of 4% chromium and upwards, possess ,a unique capacity of edge regeneration. A blade of such material will, twenty-four hours after use, reveal edge regeneration in appreciable degree. Carbon-steel blades will manifest no appreciable regeneration within twenty-four hours, nor any effeet in any period of time comparable withthat of chromium-steel blades.

The chromium steel of my invention is 'a steel alloy consisting essentially of chromium and iron; the carbon content is as specified; and the contents of" manganese, silicon, sulphur, and V phosphorus are such as are usually in non-alloyed steel. I

By way of illustration, I have caused to be fabricated to razor blades of ribbon type, by such commercial processes as I have indicated, two

The rolled ribbon of the carbon content of blanks, and these were sharpened by a commercial process, in substantially identical manner as blades of carbon steel are sharpened. The blades were. found to have equal initial sharpness with blades of carbon steel sharpened was then fabricated into razor-blade in' like manner; in service they revealed the superior qualities that have already been described;

and their term of usefulness was from 20% to 150% longer than that of the best carbon-steel blades. The wide range in the percentage just given is due to the fact that the ultimate discarding of the blades was a matter of choice with those who used themthat is to say, of the trial shavers.

I claim as my invention:

. A razor blade of ribbon type, readily susceptible to rolling hardening and sharpening, and. having the capacity of rapid recovery of sharpness,

. formed of chromium steel whose chromium content is as great as 6% and not as great as 8%, whose carbon contentis not less than 1% nor greater than 2%, whose contents of manganese,

silicon, sulphur, and phosphorus are such as are usual in non-alloyed steel,- and-whose" composition is otherwise made up of iron. 3 I

- ELBRIDGE J. 

